Method and apparatus for forming multi-layered circuit pattern

ABSTRACT

In the process of forming, on a substrate, a multi-layered circuit pattern with layers each having a portion made of the same material throughout the different layers in the direction in which the different layers are stacked, the position of nozzles with respect to the substrate when at least one of the layers is formed is shifted from that when the other layers are formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods and apparatuses for formingmulti-layered circuit patterns widely used in electronic devices.

2. Description of the Related Art

A multi-layered circuit board having a multi-layered circuit on whichsemiconductor devices, including a large-scale integration (LSI)circuit, and various electronic parts are mounted is now widely used asthe heart of electronic devices, communication devices, computers, andthe like. A typical substrate of a multi-layered circuit board to beused for such purposes is made of a composite material containing areinforcing material (e.g., ceramic or fiberglass) and plastic (e.g.,epoxide resin). Some types of substrate for a circuit board to bemounted in compact equipment, such as mobile phones and cameras, aremade of a flexible material (e.g., polyester resin or aramid resin) thatcan contribute to improved mountability of the circuit board. Recently,as the size of electronic devices decreases and their board densityincreases, multi-layered circuit boards with 8 or 16 layers have becomemainstream while, previously, most circuit boards were single-side anddouble-side boards. At the same time, as the operating speed ofelectronic circuits increases, the fineness and density of circuitpatterns are increasing rapidly.

There are various methods for forming a circuit pattern on a circuitboard. For example, Japanese Patent Laid-Open No. 11-163499 discusses amethod in which a conductive pattern forming solution (which exhibitsconductivity) and an insulating pattern forming solution (which exhibitsinsulation properties) are simultaneously ejected from a liquid ejectionhead, such as an inkjet recording head, onto the surface of a substrate,on which a conductive pattern and an insulating pattern are drawn tocreate a complete circuit pattern layer, which is then stacked on top ofone another to form a multi-layered circuit. However, since this methodcauses the mixing of the conductive pattern forming solution and theinsulating pattern forming solution at the boundary between thesesolutions and causes smearing of the circuit pattern, it is difficult toachieve a fine and high-density circuit pattern.

However, to achieve a high-density circuit board, it is essential tostack multiple layers of circuit patterns. A liquid ejection method hasan advantage over a known subtractive process in that the liquidejection method can facilitate the stacking of multiple layers, as itcan allow the formation of a circuit pattern with a thickness of onlyseveral to several tens of micrometers. However, the amount of dropletsejected from each of a plurality of nozzles in a liquid ejection headvaries. For example, as shown in FIG. 8A to FIG. 8C, the nozzleconfiguration in a nozzle assembly 1003 of a liquid ejection head 1002affects the distribution of droplets 1004 and causes variations in thethickness of a circuit pattern 1005 formed on a substrate 1001. In mostcases, variations in the amount of the droplets 1004 occur in theprocess of manufacturing the liquid ejection head 1002 and are caused bymultiple factors. Some factors may cause a random distribution of thedroplets 1004 regardless of the nozzle configuration, whereas otherfactors may cause the droplets 1004 to be distributed as shown in FIG.8A, 8B, or 8C. In FIG. 8A, the amount of the droplets 1004 at each endof the nozzle row is smaller than that in the middle thereof. In FIG.8B, the amount of the droplets 1004 in one-half of the nozzle row issmaller than that in the other half thereof. In FIG. 8C, the amount ofthe droplets 1004 gradually increases from left to right along thenozzle row. In a liquid ejection head used in typical printers andapparatuses for creating circuit boards, variations in the amount ofdroplets ejected from different nozzles are normally 20% or less, whichhas not caused any problems to date in producing a multi-layered circuitboard with four layers or less.

However, such variations in the amount of droplets cannot beaccommodated in a multi-layered circuit with ten or more layers, whichis becoming mainstream in recent years. FIG. 9A and FIG. 9B illustrate amulti-layered circuit board produced by stacking multiple circuitpatterns formed with a liquid ejection head having the above-describedconfiguration which causes variations shown in FIG. 8A. For easyunderstanding, FIG. 9A and FIG. 9B illustrate a four-layered circuitboard produced by sequentially stacking the first through fourth layerswith a liquid ejection head which can cause considerable variations,which are as high as 50%, in the amount of droplets ejected fromdifferent nozzles. This means that, in this circuit board, each layerhas a level difference of about half the thickness thereof. As thestacking process proceeds, a level difference in each layer accumulatesto a considerable level in the resulting four-layered circuit board.Generally, no significant problems arise if this resulting leveldifference is smaller than the thickness of a single circuit patternlayer. However, if a level difference which is larger than the thicknessof a single circuit pattern layer is produced in a conductive pattern,the conductive pattern will be cut, and the circuit can be easilybroken. If a level difference which is larger than the thickness of asingle circuit pattern layer is produced in an insulating pattern, theresulting poor insulation or short circuit between patterns can lead toa critical failure in the circuit board. As described above, in a liquidejection head generally used, variations in the amount of dropletsejected from different nozzles are normally 20% or less. This causes noproblems in a four-layered circuit board, as a level difference in thefour-layered circuit board is equal to or smaller than the thickness ofa single layer. However, in a circuit board with five or more layers, itis highly likely that a failure in a circuit pattern occurs, as a leveldifference in such a circuit board is larger than the thickness of asingle layer.

To produce a circuit board which extends over the length of the nozzlerow of the liquid ejection head 1002 in FIG. 8A to FIG. 8C, first, asshown in FIG. 10A, the circuit pattern 1005 corresponding to the lengthof the nozzle row is formed in a drawing area. Next, as shown in FIG.10B, the liquid ejection head 1002 is moved by the length of the nozzlerow to form a circuit pattern 1006 in the next drawing area. Thecross-sectional profile of each layer of the circuit pattern 1006 is thesame as that of the circuit pattern 1005, in which a considerable leveldifference is produced.

Variations in the thickness of such a circuit pattern are caused notonly by variations in the amount of the droplets 1004 ejected fromdifferent nozzles. As shown in FIG. 10C, unevenness on the surface ofthe circuit pattern 1005 is produced when the direction of the droplets1004 ejected from nozzles vary among the nozzles.

Again, in most cases, variations in ejection direction are caused byproblems in the process of manufacturing the liquid ejection head 1002.As in the case of variations in the amount of the droplets 1004,variations in ejection direction can occur randomly regardless of thenozzle configuration. There may be other cases where variations inejection direction occur due to the configuration of specific nozzles inthe nozzle row.

SUMMARY OF THE INVENTION

The present invention is directed to a method of forming a multi-layeredcircuit pattern which smoothes out variations in the thickness of thecircuit pattern with multiple layers stacked on a substrate. Accordingto one aspect of the present invention, a method includes forming amulti-layered circuit pattern on a substrate by ejecting solutions ontothe substrate from a liquid ejection head with a nozzle row including aplurality of nozzles while repeating relative scanning movement betweenthe liquid ejection head and the substrate in order to stack multiplelayers of the multi-layered circuit pattern. During forming themulti-layered circuit pattern, each having a portion made of the samematerial throughout the different layers in the stacking direction, theposition of nozzles with respect to the substrate when at least one ofthe different layers is formed is shifted from that when the otherlayers are formed. This can prevent the circuit pattern from beingshort-circuited or broken.

Variations in the thickness of a circuit pattern caused by variations inthe amount and direction of droplets ejected from a liquid ejection headcan be smoothed out and thus, uniformity in the thickness of amulti-layered circuit can be achieved regardless of the number of layersin the multi-layered circuit. Moreover, since level differences thatoccur at boundaries between adjacent scans can be distributed throughthe stacking of multiple layers, it is possible to provide ahigh-quality multi-layered circuit board that has excellent uniformityin thickness and thus is resistant to short-circuiting and breakingcaused by variations in the thickness of the circuit pattern.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an overall perspective view of an apparatus for forming amulti-layered circuit pattern according to at least one exemplaryembodiment of the present invention. FIG. 1B illustrates a circuitpattern and liquid ejection heads of a carriage shown in FIG. 1A.

FIG. 2 shows a process of forming a multi-layered circuit boardaccording to a first exemplary embodiment of the present invention.

FIG. 3A and FIG. 3B are cross-sectional views for illustrating amulti-layered circuit board according to the first exemplary embodiment.

FIG. 4 shows a process of forming a multi-layered circuit boardaccording to a second exemplary embodiment of the present invention.

FIG. 5 shows a process of forming a multi-layered circuit boardaccording to a third exemplary embodiment of the present invention.

FIG. 6 shows a process of forming a multi-layered circuit boardaccording to a fourth exemplary embodiment of the present invention.

FIG. 7 shows a known process of forming a multi-layered circuit board.

FIG. 8A to FIG. 8C each show variations in the amount of ejection andthe resulting thickness of a circuit pattern.

FIG. 9A and FIG. 9B are cross-sectional views of a circuit pattern drawnwith a head having variations in the amount of ejection.

FIG. 10A to FIG. 10C show problems in known examples.

FIG. 11 shows an exemplary process of forming a multi-layered circuitboard according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1A and FIG. 1B show an apparatus for forming a multi-layeredcircuit pattern according to at least one exemplary embodiment of thepresent invention. A carriage 100, serving as a main scanning unit,includes two heads (liquid ejection heads) 100 a and 100 b and theircorresponding tanks (not shown) for supplying a conductive patternforming solution and an insulating pattern forming solution to the heads100 a and 100 b. Each of the heads 100 a and 100 b has a nozzle rowincluding a plurality of nozzles. A conductive pattern forming solutionand an insulating pattern forming solution, which are both circuitpattern forming solutions, are ejected from these nozzles of the heads100 a and 100 b onto a substrate 101.

A typical conductive pattern forming solution can contain a metalcolloid, such as an aluminum (Al) colloid, a silver (Ag) colloid, or astannic oxide (SnO₂) colloid in view of their conductivity. Foruniformity and stability of a circuit pattern, a metal colloid with aparticle diameter ranging from several tens of nanometers to severalhundreds of nanometers can be used. On the other hand, while a typicalinsulating pattern forming solution contains insulating particulates,such as silica, alumina, calcium carbonate, or magnesium carbonateparticulates, any type of insulating pattern forming solution can beused, as long as it ultimately exhibits insulating properties.

The substrate 101 can be a porous ceramic substrate produced bysintering alumina, silica, aluminum nitride, barium titanate, orzirconia powder; or a porous resin film or a fiberglass substrate mostlymade of polyolefin and an inorganic filler. As will be described below,when a process of forming a circuit pattern involves a heating andfixing step or a burning step, a porous ceramic substrate, which is heatresistant, can be used.

The substrate 101 is placed on a stage 102 serving as a sub-scanningunit. The carriage 100 is configured such that it can be moved over thestage 102 by a carriage (CR) linear motor 103, serving as a drivingunit, in a main scanning direction. A line feed (LF) linear motor 102 aserves as a driving unit that moves the stage 102 in a sub-scanningdirection orthogonal to the main scanning direction. The LF linear motor102 a is secured to a surface plate 104 while maintaining its highstiffness. Therefore, the surface of the stage 102 on which thesubstrate 101 is to be placed is consistently parallel to the surface ofthe surface plate 104 even if the stage 102 is moved. The CR linearmotor 103 is secured to the upper surface of the surface plate 104 whilemaintaining its high stiffness, with a pair of base supports 105disposed between the CR linear motor 103 and the surface plate 104. Thecarriage 100 is adjusted to move along a scanning path parallel to thesurface of the surface plate 104, that is, to the surface of the stage102. The CR linear motor 103 and the LF linear motor 102 a includelinear encoders 111 and 112, respectively, and also include originsensors 113 and 114, respectively. Inputs from the linear encoders 111and 112 and origin sensors 113 and 114 are used for servo controlperformed when the CR linear motor 103 and the LF linear motor 102 amove. At the same time, the linear encoder 111 is used for controllingthe timing at which a conductive pattern forming solution and aninsulating pattern forming solution are to be ejected.

The linear encoders 111 and 112 have a resolution as high as 0.5 μm,which is sufficient for forming a circuit pattern with a width ofseveral tens of micrometers. Drawing data corresponding to a circuitpattern to be formed is transmitted from a computer (not shown)connected to the present apparatus. On the basis of the drawing datatransmitted from the computer, the LF linear motor 102 a moves the stage102 to a predetermined position. Then, as in FIG. 1B, while the carriage100 is being moved by the CR linear motor 103, a conductive patternforming solution and an insulating pattern forming solution are ejectedfrom the heads 100 a and 100 b onto the substrate 101. By repeating thisprocess, a circuit pattern including a conductive pattern and aninsulating pattern can be drawn on the substrate 101. The stage 102supporting the substrate 101 is embedded with a heater, which serves asa fixing unit that can heat each pattern and facilitate the fixing ofthe circuit pattern.

Since the present apparatus allows a circuit pattern to be drawn andimmediately fixed, layers of circuit patterns can be sequentiallystacked on top of one another to form a multi-layered circuit pattern.However, in the circuit pattern formed by the present apparatus, solventcontained in each of the solutions remains. A metal colloid fordeveloping conductivity also remains without changing its state.Therefore, to further improve the performance of a circuit board interms of electrical insulation properties and conductivity, solventremaining in the multi-layered circuit pattern formed by the presentapparatus should be completely removed. Also, for sintering the metalcolloid powder to allow conductivity to occur, a baking process shouldbe carried out by a baking apparatus that is separate from the presentapparatus.

The fixing process and the baking process do not necessarily have to beperformed according to the method described above. For example, only thefixing process can be performed every time a layer is formed, or boththe fixing process and the baking process can be performed every time alayer is formed. Alternatively, a baking process that also has theeffects of a fixing process can be performed every time a layer isformed. At the same time, the fixing unit is not limited to the heaterdescribed above.

For reference purposes, the following describes a known method forforming a multi-layered circuit pattern. As shown in FIG. 7, aconductive pattern forming solution and an insulating pattern formingsolution are ejected from the two heads 100 a and 100 b included in thecarriage 100.

First, when the stage 102 is moved to a drawing start position to form acircuit pattern A (first layer), drawing data for the first scan istransmitted from a computer. This allows the carriage 100 to startmoving across the substrate 101. While the head 100 a, serving as a“conductive” head, and the head 100 b, serving as an “insulating” head,scan across the substrate 101 in the main scanning direction (Xdirection), a conductive pattern forming solution and an insulatingpattern forming solution are ejected from the head 100 a and the head100 b, respectively, onto the substrate 101 according to the drawingdata. Upon completion of the first scan, the stage 102 is moved, for thedrawing of the next section, in a stage moving direction (Y direction)by the drawing width of the heads 100 a and 100 b (i.e., by the lengthof the nozzle rows). Then, drawing data for the second scan istransmitted from the computer, and the carriage 100 starts moving acrossthe substrate 101. As in the case of the first scan, solutionscorresponding to the drawing data for the second scan are ejected ontothe substrate 101. Thereafter, similar operations are repeated until theformation of the circuit pattern A is completed. Upon completion of thedrawing of the circuit pattern A, the heater embedded in the stage 102heats and fixes the circuit pattern A to the substrate 101. Uponcompletion of the process of fixing the circuit pattern A, the circuitpattern B (second layer) is formed over the circuit pattern A, whichserves as a substrate. Thereafter, the circuit pattern C (third layer)and the circuit pattern D (fourth layer) are sequentially stacked toform a complete multi-layered circuit pattern board with four layers.

In the known method described above, the position of the heads 100 a and100 b with respect to the substrate 101 in the sub-scanning direction (Ydirection), in other words, the drawing start position (nozzle position)in the stage moving direction is kept fixed throughout the entireprocess of forming the complete multi-layered circuit pattern. Thisknown method has advantages in that, for example, it can simplify theprocess of image editing performed by the computer and can minimize thetime required for drawing. However, in this method, when layers ofcircuit patterns are formed with the same nozzle rows, the degree ofunevenness on top of the stacked circuit patterns increases as thestacking process proceeds as shown in FIG. 9. This may lead to acritical failure in the multi-layered circuit board.

To avoid such problem, patterns formed with the same nozzle need to beprevented from overlapping in layers in the stacking direction. That is,since only a single type of circuit pattern forming material can beejected from a single nozzle, it is possible that portions formed of thesame material overlap in layers in the stacking direction. Therefore, ifa nozzle position with respect to the substrate is varied depending onthe layer, patterns formed with the same nozzle can be prevented fromoverlapping in layers in the stacking direction.

Specifically, as shown in FIG. 2 through FIG. 6, when at least onesingle circuit pattern layer is formed, the nozzle position of at leastone of the heads 100 a and 100 b can be shifted in the direction of thenozzle row that is substantially orthogonal to the main scanningdirection so that the nozzle position can be prevented from overlappingwith the nozzle position when the other circuit pattern layers areformed. For this purpose, for example, a displacement unit fordisplacing the heads 100 a and 100 b in the sub-scanning direction or inthe rotation direction is mounted on the carriage 100.

Another possible method is to use a head with a plurality of nozzle rowsfor ejecting a single material. In this case, to form layers of circuitpatterns each having a portion formed of the same material throughoutthe different layers in the stacking direction, the head is displacedalong the main scanning direction (X direction) in each layer while theposition of the head in the sub-scanning direction (Y direction) withrespect to the substrate is kept fixed throughout the process of formingdifferent layers. In other words, since a different nozzle row is usedto form a portion of the same material in each layer in the stackingdirection, variations that are unique to each nozzle row are compensatedand similar effects to those in the above-described cases can beachieved.

Specifically, FIG. 11 shows the heads 100 a and 100 b, each having fournozzle rows. In this example, a pattern P1, a pattern P2, a pattern P3,and a pattern P4 on the first layer (A), second layer (B), third layer(C), and fourth layer (D), respectively, are formed of the samematerial. The pattern P1 is formed with a nozzle row on the right end(in FIG. 11) of the head 100 b. To form the pattern P2, the heads 100 aand 100 b are displaced in the carriage moving direction (x direction).The pattern P2 can be formed with the second nozzle row from the rightend (in FIG. 11) of the head 100 b. Then, in a similar manner, the heads100 a and 100 b are displaced in the carriage moving direction (Xdirection). The pattern P3 can be formed with the third nozzle row fromthe right end (in FIG. 11) of the head 100 b, and the pattern P4 can beformed with the fourth nozzle row from the right end (in FIG. 11) of thehead 100 b. It is also possible that the heads 100 a and 100 b areconfigured to be displaced in both the X and Y directions.

First Exemplary Embodiment

As shown in FIG. 2, after the circuit pattern A (first layer) is formedand fixed to the substrate 101, before the formation of the circuitpattern B (second layer), the head 100 a, serving as a “conductive”head, and the head 100 b, serving as an “insulating” head, are displacedtogether to shift the drawing start position by ¼ of the width of theheads 100 a and 100 b. Then, in the circuit pattern C (third layer), thedrawing start position is away from the initial position by ½ of thewidth of the heads 100 a and 100 b, and in the circuit pattern D (fourthlayer), the drawing start position is away from the initial position by¾ of the width of the heads 100 a and 100 b. In other words, every timea new layer is to be formed on top of the previous one, the nozzleposition of the heads 100 a and 100 b is shifted by ¼ of the head widthin the direction of the nozzle row.

FIG. 3A shows a cross-sectional profile of the multi-layered circuitboard produced in the manner described above. The circuit pattern shownin FIG. 3A is the same as that shown in FIG. 9A. To prevent solutionsfrom being ejected onto non-drawing areas (indicated by “N” in FIG. 9A)outside the circuit pattern areas, a mask processing is performed whenthe computer creates drawing data. In the present exemplary embodiment,every time a new circuit pattern is to be formed on top of the previousone, the drawing start position is shifted by ¼ of the head width, asindicated by S1 to S4 in FIG. 9A. Therefore, raised portions in eachlayer as shown in FIG. 3B are spread out. Even if four layers arestacked, a level difference on the top surface of the four layers is assmall as the level difference in a single layer. This is because, in anysection of the circuit board, all four blocks (B1, B2, B3, and B4) ofthe entire heads 100 a and 100 b are used to form the four layers. Thus,variations in the thickness of layers depending on the nozzle positioncan be smoothed out.

Operations involved in such processing do not necessarily have to beperformed as described above. For example, the amount of shift(displacement) of the drawing start position can be ½ of the head widthin the second layer, ¾ of the head width in the third layer, and ¼ ofthe head width in the fourth layer.

The effects of the above-described smoothing achieved in thefour-layered circuit board can also be achieved in a multi-layeredcircuit board with ten or more layers. For example, if the drawing startposition is shifted by 1/S (“S” denotes the number of layers of amulti-layered circuit board) of the head width W every time before a newlayer is formed on top of the previous one, the resulting leveldifference in the complete multi-layered circuit board is consistentlyas small as the level difference in a single circuit pattern layer,regardless of the number of layers of the multi-layered circuit board.In the present exemplary embodiment, a level difference on the surfaceof the complete multi-layered circuit board appears to be as large asthe thickness of a single circuit pattern in the drawings, which areexaggerated for purposes of clear explanation. However, as describedabove, since variations in the amount of droplets ejected from differentnozzles are normally 20% or less, and since the maximum level differenceremaining in an actual multi-layered circuit board is equal to or lessthan ⅕ of the thickness of a single circuit pattern, no failure occursin the multi-layered circuit board.

In the present exemplary embodiment, to smooth out variations in thethickness of a section corresponding to the entire ejection surface ofthe heads, the amount of displacement L of the heads is set at 1/S (“S”denotes the number of layers of the multi-layered circuit board) of thelength W of the nozzle rows. However, the amount of displacement L canbe determined by L=W*N/S, where N is an integer ranging from 1 to (S-1).When variations in thickness occur randomly regardless of the positionof the heads, the amount of displacement can be determined asappropriate. Moreover, the effects of smoothing can be achieved even ifthe amount of displacement in each layer is not made consistent.

In the present exemplary embodiment, even if variations in the thicknessof a circuit pattern layer occur due to problems in the ejectionperformance of the heads, unevenness remaining on the surface of thecomplete multi-layered circuit board can be minimized. The same effectscan also be achieved with respect to level differences (such as thoseindicated by E1 to E4 in FIG. 3A) that occur at boundaries betweenadjacent scans.

Second Exemplary Embodiment

In the first exemplary embodiment, the head 100 a, serving as a“conductive” head, and the head 100 b, serving as an “insulating” head,are displaced together. However, in the second exemplary embodiment,only the head 100 b is displaced as shown in FIG. 4. In a typicalcircuit pattern layer formed by liquid ejection, all areas except thearea of a conductive pattern for connection between the terminals ofelectronic devices are occupied by the area of an insulating pattern.Since the conductive pattern is made up of fine traces with a diameterof several tens of micrometers, the circuit pattern layer is mostlyoccupied by the insulating pattern. Therefore, conductive patterns arenormally not stacked in layers and thus, there is virtually no increasein level difference on top thereof. On the other hand, most portions ofinsulating patterns, each occupying a substantial part of a singlecircuit pattern layer, are vertically stacked and thus, there is asubstantial increase in level difference on top thereof.

Therefore, in the present exemplary embodiment, every time a new layeris formed on top of the previous one, only the head 100 b, serving as an“insulating” head, is displaced by ¼ of the head width so thatunevenness on top of the insulating patterns only can be smoothed out.

As in the case of the first exemplary embodiment, the amount of shift(displacement) of the drawing start position can be, for example, ½ ofthe head width in the second layer, ¾ of the head width in the thirdlayer, and ¼ of the head width in the fourth layer. Also, whenvariations in thickness occur randomly regardless of the position of theheads, the amount of displacement can be determined as appropriate.Moreover, the amount of displacement in each layer does not have to bemade consistent.

While the present exemplary embodiment deals with a circuit patternincluding both a conductive pattern and an insulating pattern, a similareffect can be achieved in an insulating layer for completely insulatingtwo circuit patterns, that is, in a circuit pattern which only includesan insulating pattern.

When power source layers or ground layers, each of which is mostlyoccupied by a conductive pattern, are stacked in layers, a similareffect can be achieved by displacing a “conductive” head, not an“insulating” head.

Third Exemplary Embodiment

In the first exemplary embodiment described above, the head 100 a,serving as a “conductive” head, and the head 100 b, serving as an“insulating” head, are displaced by the same amount. However, in thethird exemplary embodiment, as shown in FIG. 5, the amount ofdisplacement of the head 100 a differs from that of the head 100 b. Ifthe characteristics of variations in the thickness of a circuit patterncaused by the use of the head 100 a is different from those caused bythe use of the head 100 b due to, for example, differences in themanufacturing methods of the heads 100 a and 100 b, the amount ofdisplacement appropriate for each of the heads 100 a and 100 b can beset to achieve a multi-layered circuit board with less unevenness.

For example, if the use of a “conductive” head results in variations inthe thickness of a circuit pattern as shown in FIG. 8A whereas the useof an “insulating” head results in variations as shown in FIG. 8B, theamount of displacement appropriate for the conductive head is ½ of thehead width whereas the amount of displacement appropriate for insulatinghead is ⅓ of the head width. In this case, unevenness in themulti-layered circuit board can be minimized by individually determiningthe amount of displacement for each head.

Fourth Exemplary Embodiment

As shown in FIG. 8C, there will be cases where the use of the heads 100a and 100 b causes the thickness of the resulting circuit pattern togradually increase from left to right. In such a case, as shown in FIG.6, a level difference in the resulting multi-layered circuit board canbe minimized by turning the heads 100 a and 100 b upside down every timea new layer is formed on top of the previous one. Moreover, turning thesubstrate 101, instead of the heads 100 a and 100 b, causes no problemsand can achieve a similar effect. Also, some types of variations inthickness can be smoothed out by shifting the drawing start position inaddition to turning the heads 100 a and 100 b upside down.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No.2005-181667 filed Jun. 22, 2005, which is hereby incorporated byreference herein in its entirety.

1. A multi-layered circuit pattern forming method comprising: forming amulti-layered circuit pattern on a substrate by ejecting solutions ontothe substrate from a liquid ejection head with a nozzle row including aplurality of nozzles while repeating relative scanning movement betweenthe liquid ejection head and the substrate in order to stack multiplelayers of the multi-layered circuit pattern, wherein, during forming themulti-layered circuit pattern with different layers each having aportion formed of a solution made of the same material throughout thedifferent layers in the stacking direction, the position of the nozzleswith respect to the substrate when at least one of the layers is formedis shifted from that when the other layers are formed.
 2. Themulti-layered circuit pattern forming method according to claim 1,wherein the position of the nozzles with respect to the substrate whenat least one of the layers is formed is shifted, in the direction of thenozzle row, from that when the other layers are formed.
 3. Themulti-layered circuit pattern forming method according to claim 1,wherein the position of the nozzles with respect to the substrate whenat least one of the layers is formed is reversed from that when theother layers are formed.
 4. The multi-layered circuit pattern formingmethod according to claim 1, further comprising fixing each layerformed.
 5. A multi-layered circuit pattern forming apparatus comprising:a liquid ejection head having a nozzle row including a plurality ofnozzles adapted to eject solutions for forming a multi-layered circuitpattern onto a substrate; a main scanning unit allowing for relativescanning movement between the liquid ejection head and the substrate;and a displacement unit, wherein the multi-layered circuit pattern isformed on the substrate by ejecting the solutions from the nozzles ontothe substrate while relative scanning movement of the liquid ejectionhead with respect to the substrate is repeated to stack multiple layersof the multi-layered circuit pattern, and wherein, in forming themulti-layered circuit pattern with different layers each having aportion formed of a solution made of the same material, the displacementunit shifts the position of the liquid ejection head with respect to thesubstrate when at least one of the layers is formed, from that when theother layers are formed.
 6. The multi-layered circuit pattern formingapparatus according to claim 5, wherein when shifting the position ofthe liquid ejection head, the displacement unit displaces the liquidejection head relative to the substrate in the direction of the nozzlerow, and wherein an amount of displacement (L) can be determined byL=W*N/S, where (W) is a length of the nozzle row, (S) is a number oflayers of the multi-layered circuit board, and (N) is an integer rangingfrom 1 to (S-1).